Azopyridine compounds as fog inhibitors for photographic emulsions



Patented Mar. 23, 1954 2,673,152 AZOPYRIDINE COMPOUNDS AS FOG IN HIBI- TORS FOR Charles F. H.

Conn.,

PHOTOGRAPHIC EMULSION S Allen and John R. Byers, Jr., Rochester, N. Y., and Robert H. Sprague, Portland,

assignors to Eastman Kodak Company, Rochester, ,N. Y.,.a corpo ration of New. Jersey No Drawing. Application February 16, 1953, Serial No. 337,234

11 Claims. 95--7) This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions and to photographic emulsions containing them.

It is known that silver sensitized ing formula used and increases with the temperature and duration of development.

It is an object of the invention to :provide novel anti-fogging and fog-inhibiting compounds for emulsions. A further object is to provide antifogging agents which stabilize the initial .sensi- These ing into a silver halide emulsion small amounts of halogenated 2,2'-azopyridine compounds such as 5,5-dichloro-'2;2'-azop-yridine, 5,5"-7dibromo- 2,"2'-azopyridine, 5,5-diiodo-2;2-azopyridine, chloro-2,2 -azopyridine, 3,3 ,5 ,5" -.tetra'chl'oro -i2;2f azopyridine and 5,5'-dichloro-3,3-dimethyl-2;2'- azopyridine.

Similar azoxy compounds such as 4,4'-,dicliloro- 2, -azoxypyridine exhibit fog-inhibiting proper- J. Gen. Chem. (U. S. S. 'R.) (1940) C. A. .35, 40237 (1941.)

A wide variety of compounds have been used in photographic emulsions .to inhibit fog. For example, mercaptopyrimidine compound containing a 5-arylazo group are described by Sheppard et a1. U. S. Patent. 2,304,962 .for this purpose.

2 Similarly, Davey et a1. U, S. Patent 2,273,502 discloses amino hydroxy pyrimidines as anti-fogsuch as 2,2'-azopyrimidine, 2,2'-azopyridine, 3,3- azoquinoline, 4,4-dimethyl-2,2'-azothiazole, and 6-azobenzimidazole have little or no anti-foggant genated amino pyridines, for example, .5-chloro- -amino pyridine and 3,5-ohloro-2-amino pyridine hydrochloride, in photographic developers However, our work shows that the halogenated amino pyridines such as 5-iodo-2-amino pyridine and 5- chloro-2-amino pyridine do not inhibit fog for- .our invention. Moreover, the compounds invention such as 5,5-dichloro-2,2'-azopyridine do not function as anti-foggants when tures, however,

separate operations (1) the emulsidigestion or ripening of the silver halide, (2) the freeing of the emulsion .irom exsalts usually by washing, (3) the second digestion or after-ripening to obtain increased sensitivity. (Mees, "The Theory of the Photographic Process, 1942.) We prefer to add the fog-inhibiting agents after the final digestion or after-ripening although they may be added before digestion. The most'useful range of concentration of the fog inhibitor compounds of our emulsionsis from about 0.0025 to about 0.1 milligram per mol of silver halide in the emulsions as illustrated by .the following examples. The quantity will, of course, vary, for example, -.de-

V and X-ray emulsions.

was made employed, for samples A-I-I a high speed bromo-iodide emulsion, and for samples I-N a medium-speed bromoiodide emulsion. The samples were exposed as usual on an Eastman type 13 Sensitometer and developed for five minutes in a developer of the following composition:

V Grams Monomethyl paraminophenol sulfate 2.5 Sodium sulfite 3O Hydroquinone 2.5 Sodium metaborate Potassium bromide 0.5

Water te one liter In the case of the latent image keeping tests supplied below for samples A-H, it will be apparent that exposures were made on these samples in the same manner on the sensitcmeter but the exposed samples were incubated at 120 F. before 10 The test from which the following tabulation antifoggant amount.

We also contemplate as a part of our invention those cases where it is desirable to coat the antiioggant in a colloid layer such as gelatin on either or both sides of or also in a silver halide emulsion layer, so that the antifoggant is contiguous to the silver halide emulsion. In these cases'we use the same or a slightly greater ratio of the halogenated2,2-azopyridine compounds to silver halide than when the compounds are present in the emulsion.

What we claim is:

- 1. A light-sensitive photographic emulsion comprising silverhalide and a halogenated 2,2- azopyr-idine in antifogg ant amoun 2. A light-sensitive photographic emulsion comprising silver halide and a member selected from the group consisting of 5,5'-dichloro-2,2'- azopyridine, 5,5-dibromo-2,2'-azopyridine, 5,5- diiodo-2 ,2 -azopyridine, 5-chloro-2,2' -azopyrldine, 3 ,3 ,5 ,5 -tetrachlo-2,2 -azopyridine, and 5,5-dichloro-3,3 -dimethyl-2,2'-azopyridine in 3. A light-sensitive photographic emulsion comprising silver halide and a chlorinated 2,2- azopyridine in antiioggant amount.

4. A light-sensitive photographic emulsion comprising silver halide and a brominated 2,2- azopyridine in antifoggant amount.

5. A light-sensitive photographic emulsion comprising silver halide and an iodated 2,2'-az0- pyridine in antifoggant amount.

processing.

, Mgs. per Fresh Tests 1 wk. 120 F.

f Compound Emulsion Speed Gamma Fog Speed Gamma Fog A 3, 200 0. 97 0. 06 l, 400 0. 77 0 3, lOO 0. 93 05 2, 200 0. 87 16 2, 500 1. 00 04 2. 100 0.92 12 l, 950 1.11 05 1, 650 0. 96 ll 2, 650 0.99 05 2, 700 0. 85 14 2, 450 1. 02 05 2, 100 0. 97 12 2,000 1.06 05 1,750 0.97 12 2, 400 1. 03 05 l, 750 0.97 20 l, 620 0. 95 07 1,081) i 0.90 22 1, 600 0.90 06 l. 620 0. 94 16 do .r 1,550 0.88 .06 1,050 1.15 14 L 3,3-dimethyl-5,5-dichloro-2,2- 2 200 l. 06 .96 2, 500 1. 05 16 azopyridine. M do 6 1, 700 1. 11 O5 2, 450 1. 01 09 N 3,3',5,5 tetra chloro 2,2 azo 06 2, 550 1. l9 08 2, 350 0. 87 16 pyridine. r

Latent Image Keeping, 1 wk. 120 F.

- The fag-inhibiting agents which we have described may be used in various kinds of photographic emulsions. In addition to being useful inordinary non-sensitized emulsions they may also be used in orthochromatic, panchromatic If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride and mixtures of these. The dispersing agents may be gelatin or other colloid such as collodion, ,al-

bumen, cellulose organic derivatives or synthetic resins.

50 comprising silver i 6. A light-sensitive photographic emulsion halide and 5,5'-dichloro-2,2'- azopyridine in antifoggant amount.

' '7. A light-sensitive photographic emulsion comprising silver halide and 5.5-dibromo-2,2'- azopyridine in antifoggant amount.

8. A light-sensitive photographic emulsion comprising silver halide and 5,5-diiodo-2,2'-azopyridine in antifoggant amount.

9. A light-sensitive photographic comprising silver halide and 5-chloro-2,2-azopyridine in antifoggant amount.

10. A light-sensitive photographic emulsion comprising silver halide and 3,3',5,5'-tetrachloro- 2,2'-'azopyridine in antifoggant amount.

11. A light-sensitive photographic element comprising a silver halide emulsion layer and an organic colloid layer contiguous to said emulsion .layer, at least one of said layers containing a halogenated 2,2-azopyridine.

CHARLES F. H. ALLEN. JOHN R. BYERS, JR- ROBERT H. SPRAGUE.

No references cited.

emulsion 

1. A LIGHT-SENSITIVE PHOTOGRAPHIC EMULSION COMPRISING SILVER HALIDE AND A HALOGENATED 2,2''AZOPYRIDINE IN ANTIFOGGANT AMOUNT. 